Tests based on the binding of one biomolecule to another are well known. For example, the presence of a particular nucleic acid sequence in a solution can be ascertained by detecting the binding of the nucleic acid to a substrate having an immobilized nucleic acid of the complementary sequence. Tests based on such hybridized binding are particularly attractive in that they allow one to test an unknown sample against a large number of possible matching candidates.
In many test systems such as nucleic acid testing systems, the presence of a bound target molecule requires a very high degree of sensitivity, since the amount of material that is bound to the immobilized “probes” is small. Prior art systems typically rely on special fluorescent labels on the targets or on intercalation dyes that selectively bind to double stranded nucleic acids. Both of these methods require the use of very sensitive fluorescence scanners that represent a high capital investment.
In addition to high sensitivity, assays that allow the detection of multiple dyes are particularly useful. The special fluorescent labels mentioned above can, in principle, be formulated to have different fluorescent bands to allow the measurement of several target species at a time. However, the cost of creating a large number of such dyes with fluorescent bands that are easily distinguished from one another is prohibitive.
Broadly, it is the object of the present invention to provide an improved binding assay that can provide the required sensitivity without the need for expensive fluorescence scanners.
These and other objects of the present invention will become apparent to those skilled in the art from the following detailed description of the invention and the accompanying drawings.